Hydraulic machines utilize fluid power for performing simple as well as heavy duty tasks. Pressurized hydraulic fluid, i.e., oil, is transmitted throughout the machine to various hydraulic pumps, valves, and motors to drive the machine. The power steering and power brakes in vehicles, and the power train in construction equipment, are examples of hydraulic systems in such machines.
Filters are incorporated into most hydraulic systems for removing metal particles from the oil, along with other contaminants. Blockage of the filter creates a restriction to hydraulic fluid flow, leading to pump noise and other problems. Further, during cold temperature working conditions, hydraulic fluid becomes more viscous, which increases the amount of resistance to flow in the reservoir. The hydraulic pump works harder to draw this more viscous fluid. The colder temperatures also increase the number of air bubbles in the fluid, and this affects the hydraulic pump, resulting in noisy operation. Most filters incorporate valves to ease hydraulic fluid pressure inside the filter during cold temperature operations. In practice, these valves have met with little success, and have caused increased noise at low temperature operation.
Thus a need exists for a hydraulic filter with mechanisms for improving cold temperature operations of hydraulic pumps.